fix the fix for bug #70976 (imagerotate)

Author: remicollet

ext/gd/libgd/gd_interpolation.c

@@ -2154,15 +2154,15 @@ gdImagePtr gdImageRotateInterpolated(const gdImagePtr src, const float angle, in
 {
 	const int angle_rounded = (int)floor(angle * 100);
 
-	if (bgcolor < 0 || (!src->trueColor && bgcolor >= gdMaxColors)) {
+	if (bgcolor < 0) {
 		return NULL;
 	}
 
 	/* impact perf a bit, but not that much. Implementation for palette
 	   images can be done at a later point.
 	*/
 	if (src->trueColor == 0) {
-		if (bgcolor >= 0) {
+		if (bgcolor < gdMaxColors) {
 			bgcolor =  gdTrueColorAlpha(src->red[bgcolor], src->green[bgcolor], src->blue[bgcolor], src->alpha[bgcolor]);
 		}
 		gdImagePaletteToTrueColor(src);

ext/gd/tests/bug70976.phpt

@@ -6,8 +6,8 @@ Bug #70976 (Memory Read via gdImageRotateInterpolated Array Index Out of Bounds)
 ?>
 --FILE--
 <?php
-$img = imagerotate(imagecreate(1,1),45,0x7ffffff9);
+$img = imagerotate(imagecreate(10,10),45,0x7ffffff9);
 var_dump($img);
 ?>
 --EXPECTF--
-bool(false)
+resource(5) of type (gd)